This invention relates in general to plastic pipe fittings and more particularly to a Tee fitting of the type commonly used with plastic irrigation pipe and other plastic pipe.
Tee fittings are used in a variety of plastic pipe systems such as those used to supply water for irrigation of agricultural fields. Often, the stem of the fitting must be threaded to provide a threaded connection with another plastic conduit. This type of Tee fitting is conventionally formed by using a main conduit body having its ends suitably shaped to connect with the main flow line. The wall of the main body is provided with a circular opening and a hollow neck which projects outwardly from the pipe wall around the opening. A spout is fitted inside of and glued to the neck at one end. The other end of the spout fits inside of and is glued to an adapter which is internally threaded for connection with an externally threaded pipe.
The main problem with the conventional plastic Tee fitting is that the connection between the spout and neck is relatively weak. Because the neck projects only a short distance, there is little surface area available for the glue joint between the spout and neck, and this joint is susceptible to failure when side forces are applied. Also, the adapter is located well outwardly of the neck with only the spout extending between the neck and adapter. The overall result is that the strength of the conventional Tee fitting is less than satisfactory in many applications and particularly where there is a likelihood of encountering significant side loads.
In recent years, Tee fittings have been available in a stronger construction in which an insert is used to strengthen the joint between the neck and spout. The insert essentially lengthens the neck and is glued to the inside surface of the neck to provide a glue joint having the same surface area as in the conventional construction. The spout is sleeved around and glued to the outside surfaces of both the neck and insert to provide increased strength due to the greater area of the glue joint. The outer end of the spout is fitted in and glued to the threaded adapter in the same manner as in the conventional Tee fitting. Although this construction does strengthen the fitting, it has not completely solved the problem of failure when heavy side blows are applied. Again, only the spout extends between the neck and adapter and only a single glue joint connects the adapter to the end of the spout. In addition, this type of fitting requires a specially shaped spout.
The present invention is directed to an improved plastic Tee fitting which exhibits greater strength than the fittings that have been available in the past. In accordance with the invention, an internally threaded adapter is arranged end to end with the neck on the side of the main conduit body, and the joint between the neck and adapter is strengthened and reinforced on both the inside and outside. A cylindrical insert is received inside of the neck and adapter and is glued to each. On the outside, a spout is sleeved closely around and glued to both the neck and adapter. A flange or saddle on the spout is glued to the outside surface of the main body to further strengthen the fitting. Due to the increased surface areas that are glued together in the area of the joint and the decreased distance of the adapter from the neck, the fitting of the present invention is better able to withstand side forces than the Tee fittings that have been available in the past.